Method and system for reducing the effect of signal-interference in null areas caused by one or more antennas

Abstract

In wireless communications, a method and system for enhancing signal decoding capability in null areas uses dithering to break up or modify the null areas. The null areas form in overlapping regions of the beams of two antennas or in overlapping regions of a single signal that is subject to multipath. Dithering is used to spread the null areas over a wider region so that a WTRU in an overlap region will not statically remain within a null area.

1. In a wireless telecommunications network in which a plurality of base stations may simultaneously transmit signals to wireless transmit and receive units (WTRUs), a method comprising:
 determining whether a static null area exists in a region covered by the base stations, the static null area being caused by interference between two or more overlapping signals; and 
 if it is determined that a static null area exists in the region, effecting a dithering change in a transmission parameter of one of said transmit signals in the region in accordance with a control signal with synchronization time marks for aligning the dithering change, thereby shifting the static null area. 
 
   
   
     2. The method of  claim 1 , wherein the dithering change includes altering boresight of transmission of at least one of the overlapping signals, thereby shifting the null areas so that a wireless transmit and receive unit (WTRU) within the overlapping region will not statically remain within a null area. 
   
   
     3. The method of  claim 1 , wherein the dithering change includes altering transmission amplitude of at least one of the overlapping signals, thereby shifting the null areas so that a wireless transmit and receive unit (WTRU) within the overlapping region will not statically remain within a null area. 
   
   
     4. The method of  claim 1 , further comprising controlling signal processing of a base station to generate a beam formed transmission pattern, the beam formed transmission pattern dithered by altering a boresight of transmission of a signal transmitted by the base station. 
   
   
     5. The method of  claim 4 , wherein the beam formed transmission pattern is dithered by altering an amplitude of transmission of the base station, thereby shifting null areas so that a wireless transmit and receive unit (WTRU) within the overlapping region will not statically remain within a null area. 
   
   
     6. A base station for use in a wireless telecommunications network wherein a plurality of base stations may simultaneously transmit signals which overlap, the base station comprising:
 means for determining whether a static null area exists in a region covered by a base station, the static null area being caused by interference between two or more overlapping signals; and 
 a circuit for effecting a dithering change in a transmission parameter of a signal transmitted from the base station in accordance with a control signal with synchronization time marks for aligning the dithering change, thereby shifting the static null area in the region covered by the base station. 
 
   
   
     7. The base station of  claim 6 , further comprising a circuit for determining a requirement for reducing interference nulls within a region where a signal transmitted from the base station overlaps with a signal transmitted from other simulcasting base stations. 
   
   
     8. The base station of  claim 6  wherein the dithering change alters the location of null areas resulting from the overlapping signals. 
   
   
     9. The base station of  claim 6  wherein the circuit for effecting a dithering change shifts a transmission beam of the base station, thereby shifting the null areas so that a wireless transmit and receive unit (WTRU) will not statically remain within a null area. 
   
   
     10. The base station of  claim 6 , wherein the dithering change includes altering a boresight of transmission of the base station, thereby shifting the interference null areas so that a wireless transmit and receive unit (WTRU) within the overlap region will not statically remain within an interference null area. 
   
   
     11. The base station of  claim 6 , wherein the dithering change includes altering transmission amplitude of the base station, thereby shifting the interference null areas so that a wireless transmit and receive unit (WTRU) within the overlap region will not statically remain within an interference null area. 
   
   
     12. The base station of  claim 6 , wherein the dithering change includes altering a boresight and amplitude of transmission of the base station, thereby shifting the interference null areas so that a wireless transmit and receive unit (WTRU) within the overlap region will not statically remain within an interference null area. 
   
   
     13. The base station of  claim 6 , further comprising:
 the base station provided as part of an array of base stations; and 
 a circuit for controlling signal processing of the array of base stations in order to generate a beam formed transmission pattern from each base station, the beam formed transmission pattern dithered by altering a transmission parameter of the base station. 
 
   
   
     14. In a radio communications network, a method of operating a base station in coordination with other simulcasting base stations within reception proximity, the method comprising:
 determining whether a static null area exists in a region covered by a base station, the static null area being caused by interference between two or more overlapping signals transmitted from the base station and other simulcasting base stations; and 
 if it is determined that a static null area exists in the region, effecting a dithering change in a transmission parameter of a signal transmitted by the base station in accordance with a control signal with synchronization time marks for aligning the dithering change, thereby altering null areas resulting from the overlapping signals. 
 
   
   
     15. The method of  claim 14 , wherein the dithering change includes altering boresight of transmission of the signal transmitted by the base station, thereby shifting the null areas so that a wireless transmit and receive unit (WTRU) within the overlap region will not statically remain within a null area. 
   
   
     16. The method of  claim 14 , wherein the dithering change includes altering transmission amplitude of a signal transmitted from the base station, thereby shifting the null areas so that a wireless transmit and receive unit (WTRU) in the overlapping region will not statically remain within a null area. 
   
   
     17. The method of  claim 14 , wherein the dithering change includes altering an amplitude and boresight of transmission of a signal transmitted from the base station, thereby shifting the null areas so that a wireless transmit and receive unit (WTRU) in the overlapping region will not statically remain within a null area. 
   
   
     18. The method of  claim 14 , further comprising controlling signal processing of a base station to generate a beam formed transmission pattern, the beam formed transmission pattern dithered by altering a transmission parameter of a signal transmitted by the base station. 
   
   
     19. In a wireless telecommunications network having a plurality of base stations that may simultaneously transmit to wireless transmit and receive units (WTRUs), a method comprising:
 determining whether a static null area exists in a region covered by a base station, the static null area being caused by interference between two or more overlapping signals transmitted from the base station and from at least one other base station; and 
 effecting a dithering change in a transmission parameter of a signal in the overlapping region in accordance with a control signal with synchronization time marks for aligning the dithering change, thereby altering a pattern of interference null areas resulting from the overlapping signals. 
 
   
   
     20. The method of  claim 19 , wherein the dithering change includes altering a boresight of transmission of the signal transmitted from the base station, thereby shifting the null areas so that a wireless transmit and receive unit (WTRU) in the overlapping region will not statically remain within a null area. 
   
   
     21. The method of  claim 19 , wherein the dithering change includes altering transmission amplitude of the signal transmitted from the base station, thereby shifting the null areas so that a wireless transmit and receive unit (WTRU)) in the overlapping region will not statically remain within a null area. 
   
   
     22. The method of  claim 19 , wherein the dithering change includes altering transmission amplitude and boresight of transmission of the signal transmitted from the base station, thereby shifting the null areas so that a wireless transmit and receive unit (WTRU) in the overlapping region will not statically remain within a null area. 
   
   
     23. The method of  claim 19 , further comprising controlling signal processing of a base station to generate a beam formed transmission pattern, the beam formed transmission pattern dithered by altering a transmission parameter of a signal transmitted by the base station. 
   
   
     24. A method for reducing interference effects generated by overlapping signals transmitted by at least one base station in a wireless telecommunications network, the method comprising:
 determining a requirement to reduce static null areas in regions covered by a the at least one base station having overlapping signals, the static null area being caused by interference between two or more overlapping signals; 
 in the event of the requirement to reduce null areas, determining a dithering parameter to shift the null areas so that a WTRU within a region of overlapping signals does not statically remain within the null area; and 
 controlling the at least one base station in the network by distributing a control signal with synchronization time marks in order to align a dithering change resulting from implementation of the dithering parameter. 
 
   
   
     25. The method of  claim 24  wherein the overlapping signals are transmitted from a single base station and occur as a result of a single signal transmitted from the base station being subject to multipath. 
   
   
     26. The method of  claim 24  wherein the overlapping signals are separately broadcast from at least two base stations. 
   
   
     27. A base station for use in a wireless telecommunications network and having an antenna whose signal is subject to multipath, the base station comprising:
 means for determining whether a static null area exists in a region covered by the base station, the static null area being caused by interference between two or more overlapping signals; and 
 a circuit for effecting a dithering change in a transmission parameter of the signal in a region having overlapping signals in accordance with a control signal with synchronization time marks for aligning the dithering change, thereby shifting the null area in the region covered by the base station. 
 
   
   
     28. The base station of  claim 27 , further comprising a circuit for determining a requirement for reducing interference nulls within the overlapping region. 
   
   
     29. The base station of  claim 27  wherein the dithering change alters the location of null areas resulting from the overlapping signals. 
   
   
     30. The base station of  claim 27  wherein the circuit for effecting a dithering change shifts a transmission beam of the base station, thereby shifting the null areas so that a wireless transmit and receive unit (WTRU) will not statically remain within a null area. 
   
   
     31. The base station of  claim 27 , wherein the dithering change includes altering a boresight of transmission of the base station, thereby shifting the interference null areas so that a wireless transmit and receive unit (WTRU) within the overlap region will not statically remain within an interference null area. 
   
   
     32. The base station of  claim 27 , wherein the dithering change includes altering transmission amplitude of the base station, thereby shifting the interference null areas so that a wireless transmit and receive unit (WTRU) within the overlapping region will not statically remain within an interference null area. 
   
   
     33. The base station of  claim 27 , wherein the dithering change includes altering a boresight and amplitude of transmission of the base station, thereby shifting the interference null areas so that a wireless transmit and receive unit (WTRU) within the overlapping region will not statically remain within an interference null area. 
   
   
     34. The base station of  claim 27 , further comprising:
 the base station provided as part of an array of base stations; and 
 a circuit for controlling signal processing of the array of base stations in order to generate a beam formed transmission pattern from each base station, the beam formed transmission pattern dithered by altering a transmission parameter of the base station. 
 
   
   
     35. In a wireless telecommunications network having a plurality of base stations that may simultaneously transmit to wireless transmit and receive units (WTRUs), a method comprising:
 determining whether a static null area exists in a region covered by a base station, the static null area being caused by interference between two or more overlapping signals which are multipath components transmitted from the same base station; and 
 effecting a dithering change in a transmission parameter of the signal transmitted from the base station in accordance with a control signal with synchronization time marks for aligning the dithering change, thereby shifting the null area in the region covered by the base station. 
 
   
   
     36. The method of  claim 35 , wherein the dithering change includes altering a boresight of transmission of a signal transmitted from the base station, thereby shifting the null areas so that a wireless transmit and receive unit (WTRU) in the overlapping region will not statically remain within a null area. 
   
   
     37. The method of  claim 35 , wherein the dithering change includes altering transmission amplitude of a signal transmitted from the base station, thereby shifting the null areas so that a wireless transmit and receive unit (WTRU) in the overlapping region will not statically remain within a null area. 
   
   
     38. The method of  claim 35 , wherein the dithering change includes altering transmission amplitude and boresight of transmission of a signal transmitted from the base station, thereby shifting the null areas so that a wireless transmit and receive unit (WTRU) in the overlapping region will not statically remain within a null area. 
   
   
     39. The method of  claim 35 , further comprising controlling signal processing of a base station to generate a beam formed transmission pattern, the beam formed transmission pattern dithered by altering a transmission parameter of a signal transmitted by the base station. 
   
   
     40. A method for reducing interference effects generated by overlapping signals transmitted in a wireless telecommunications network, the method comprising:
 determining a requirement to reduce static null areas in regions having overlapping signals; 
 in the event of the requirement to reduce null areas, determining a dithering parameter to shift the null areas so that a WTRU within a region of overlapping signals does not statically remain within a null area; 
 controlling a base station in the network according to the dithering parameter so as to effect a dithering change; and 
 distributing a control signal to at least one base station with synchronization time marks in order to align the dithering change.